Calcium silicate shaped bodies are lightweight, have excellent heat insulating properties, high fire resistance and various other characteristics, and are therefore widely used.
In the field of heat insulating materials and the like, there is a demand for calcium silicate shaped bodies of improved heat insulating properties in recent years.
Accordingly processes have been proposed for giving improved heat insulating properties by incorporating various substances into calcium silicate shaped bodies.
U.S. Pat. No. 3,001,882 discloses a process for producing a shaped body having improved heat insulating properties at a high temperature (288.degree. C., 550.degree. F.) by adding a chemically inactive substance to a starting slurry composed of a calcareous material, a siliceous material and water, shaping the slurry, and subjecting the green shaped body obtained to a hydrothermal synthesis reaction. With this process, however, the strength of the shaped body tends to decrease with an increase in the amount of inactive substance used. Especially when the amount exceeds 20% by weight of the shaped body, the shaped body obtained is exceedingly low in strength and is not usable. Thus, although the process wherein the green shaped body is subjected to hydrothermal synthesis reaction gives improved heat insulating properties at a high temperature, the improvement is inherently limited and is still insufficient, while the process fails to afford improved heat insulating properties at low temperatures of up to about 200.degree. C.
Unexamined Japanese Patent Publication No. SHO 58-145652 discloses (a) a process for producing a shaped body by preparing a slurry of calcium silicate crystals first, adding to the slurry a substance which absorbs or diffuses radiant energy, shaping the resulting slurry and drying the shaped body: (b) a process for producing a shaped body of calcium silicate crystals by preliminarily reacting a starting slurry to obtain a slurry of C-S-H (I) which is a precursor of crystalline calcium silicate, adding the above substance to the slurry, shaping the slurry and curing the green shaped body with steam: and (c) a process for producing a shaped body of calcium silicate crystals by preliminarily reacting a starting slurry containing the above substance to obtain a slurry of C-S-H (I), shaping the slurry and curing the green shaped body with steam. However, the processes (a) and (b) are unable to produce a useful lightweight shaped body because of seriously reduced strength if more than 20% by weight of the substance is present based on the shaped body, while the process (c) encounters difficulties in producing a shaped body itself owing to deformation or shrinkage if not smaller than 15% by weight of the substance is used. Further although these processes achieve some improvement in the heat insulating properties of the shaped body at high temperatures of at least 300.degree. C., the improvement is still insufficient, whereas the processes fail to attain any substantial improvement in the heat insulating properties at low temperatures of up to about 200.degree. C.